The Effect of Processing On Starch Availability

The way that corn is processed has a tremendous effect on the amount that is digested and where in the digestive tract it is digested. Whether your corn is flaked or ground, the degree to which it is processed can make a huge difference in performance. With today’s’ corn prices this is a critical factor in the profitability of your dairy.

Flake weight is steam flaked corn and is very important in determining the availability of the starch for digestion in the rumen. Flakes can weigh anywhere from 20-30 lbs per bushel. Above 30 lbs per bushel would be considered steam rolled corn. Flake weight is controlled by three things, time in the steam cabinet, roller settings and speed of rolling. Time in the steam cabinet is the most important. The longer the corn is in the steam cabinet, the more moisture is absorbs, and the easier it is to get the desired thickness through the rolls.

There are performance differences generated from the different flake weights. The lower the flake the more digestion takes place in the rumen. This is where we want as much starch digested as possible. Starch digested in the rumen produces microbial protein. Starch that is digested in the intestine is still producing energy, but more bypass protein must be fed to compensate for loss of microbial protein. For every 4 lbs increase in flake weight, you lose ¼ lb production from energy and 1 lb from microbial protein. So when we go from an ideal 28 lb flake to a 38 lb steam roll, we lose 1.5 lbs of ME milk and 4 lbs of MP milk.

Ground corn is evaluated by the fineness of grind. This is measured by shaking through a series of screens to determine micron size. The smaller the micron size, the more surface area available for the starch digesting rumen bugs to “do their thing”. The larger particles have more of a chance to pass through the rumen and into the manure.

Most recommendations are for corn to be ground to 600-700 microns in size. There is a lot of corn being fed today that is not ground this fine. Research has shown that corn with an average micron size of 1100, has a rumen digestibility of 50%. Corn ground to 400 microns increases in rumen digestibility to over 90%. This equates to over 4 lbs difference in milk production.

Many people will be concerned about acidosis with more starch being digested in the rumen. There is a simple answer to this problem, we can feed less corn. If more is available for microbial production in the rumen we can simply feed less, make the same milk, and be more efficient.

A quick way to check for poor corn digestibility, is to look at manure. If you see corn in the manure, there is corn not being digested. The next step would be to have a starch assay done on a sample of your manure. Starch in manure should be less than 3%. There will usually be less starch from a flake or a roll than from ground corn. The flaked corn will be digested more thoroughly in the intestine. You still want a low flake weight, for increased performance.

How do we measure the micron size or flake weight. Micron size needs to be measured through a series of screens and the average particle size calculated. Flake weight can be measured with a special flake weight scale.

If you would like to learn more about increasing the production of your dairy farm please call us today at 1-208-308-8612!